Medical tubing having variable characteristics and method of making same

ABSTRACT

The invention primarily is directed to a medical tubing adapted for insertion into a body tissue or cavity and method of manufacturing different variations of the tubing along a length of the tubing. The tubing comprises a plurality of individual, discrete, generally ring-shaped elements arranged in series and fused or bonded together forming a continuous tubular structure. The ring-shaped elements may include a combination of flexible and rigid ring-shaped elements assembled along different portions or sections of the tubular structure. In another aspect of the invention, the medical tubing may further comprise a secondary lumen and a pull wire to control the tubular structure. In another aspect of the invention, the ring-shaped elements may vary in diameter and/or composition in different portions or sections of the tubular structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/766,138, filed on Jan. 28, 2004, the disclosure of which is herebyincorporated by reference as if set forth in full herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to medical devices and, morespecifically, to medical tubing adapted for insertion into a body tissueor cavity having variable characteristics and method of making same.

2. Discussion of Related Art

Medical tubing includes tubing used as catheters, drain tubes, accessports, endoscope bodies and the like. The requirements for each type ofmedical tubing will depend on its use. In particular, a specific lengthof medical tubing may vary depending on each application. For example, aspecific length of medical tubing may need to be very flexible and yetpushable, or it may need to be thin-walled and yet kink-resistant. Inaddition, the tubing may need to exhibit these properties in onlyspecific regions.

Most medical tubing is extruded from a single plastic material in acontinuous forming process. Certain characteristics or variations may beimparted to the extruded tubing by altering the speed or the tension ofthe extruded material as it exits and cools from the extrusion machine.However, the variations are limited by the fact that a single materialis extruded. Recent advances in extrusion technology have allowed theco-extrusion of multiple materials. This provides some usable variationsin extruded tubing. Nevertheless, this is still a linear process and isstill limited by the continuous flow of the extruded materials.

Accordingly, there is a need for a medical tubing having a length withvariable characteristics and a method of making the tubing such thatvariations can occur along the length of the manufactured tubing. Forinstance, a length of the tubing may be rigid for a length, becomesflexible for a length and then becomes rigid again for another length.It is also desirable to have large variations in the diameter of thetubing. In another application, there may be a need for a tube that isextremely kink-resistant in a specific region. Kink-resistance with verythin walls is not obtainable through the current extrusion processes.

SUMMARY OF THE INVENTION

The invention is primarily directed to a medical tubing adapted forinsertion into a body tissue or cavity and method of manufacturingdifferent variations of the tubing along a length of the tubing. In oneaspect of the invention, the medical tubing includes a length withvariable characteristics, the tubing comprising a plurality ofindividual, discrete, generally ring-shaped elements arranged in seriesand fused or bonded together forming a continuous tubular structure. Thering-shaped elements may be formed of a thermoplastic or a thermosetmaterial. The ring-shaped elements may include plastic rings, metallicrings, un-reinforced plastic rings and/or metal reinforced plastic ringsassembled along the length of the tubular structure to provide variableflexibility and kink-resistance. The tubular structure may be bent,twisted or curved without kinking. The tubular structure may have across-section that is circular, oval, rectangular, triangular, hexagonalor any geometric shape. The ring-shaped elements may have differentflexural modulus. The ring-shaped elements may include a combination offlexible and rigid ring-shaped elements assembled along differentportions or sections of the tubular structure, wherein as the tubularstructure is bent, twisted or curved, the rigid ring-shaped elementsprovide reinforcement to maintain the size and shape of the lumen andthe flexible ring-shaped elements operate to stretch and compress toprevent kinking. The ring-shaped elements may be metallic and may bebonded with a resilient, flexible elastomeric adhesive, wherein thering-shaped elements may have different lengths and may be fused closeror further apart to one another depending on the characteristics of aportion or section of the tubing.

In another aspect of the invention, the medical tubing may furthercomprise a secondary lumen and a pull wire to control the tubularstructure. It is appreciated that at least one of the ring-shapedelements may be truncated to provide a bending bias. The truncatedelements may comprise of alternating flexible ring-shaped elements andrigid ring-shaped elements. In yet another aspect of the invention, thering-shaped elements may vary in diameter and/or composition indifferent portions or sections of the tubular structure. In anotheraspect of the invention, some of the ring-shaped elements may beradiopaque, or the ring-shaped elements may comprise of different colorsto operate as indicators along the tubular structure. Applications ofthe medical tubing of the invention include AV introducers, urologicalsheaths, ureteral access sheaths, urethral and bladder access sheaths,kidney access sheaths, ureteral stents, trocar cannulas,suction/irrigation tubing, insufflation tubing, vacuum tubing, splitsheath introducers, tracheostomy tubes, intubation tubes, gastronomytubes, jujenostomy tubes, extracorporeal retrogradecholangeopancreatography catheters, endoscope shafts, drainage tubes,guide catheters, hydrocephalic shunts, guidewires, angioplasty anddilation balloons, vascular grafts, cholangiography catheters, vascularembolectomy/thrombectomy catheters, and central venous catheters.

In another aspect of the invention, a method of manufacturing themedical tubing having a length with variable characteristics isdisclosed, the method comprising the steps of placing a plurality ofring-shaped elements upon a support member or mandrel in a seriesarrangement, and heating the plurality of ring-shaped elements to fusethem together over the support member or mandrel. The method of theinvention may further comprise the step of placing the plurality ofring-shaped elements upon a second support member or mandrel before theheating step to subsequently form a second lumen or control tube to thetubular structure. This method may further comprise the step of forminga control tube over the assembled ring-shaped elements prior to theheating step. The control tube may comprise at least one of glass,silicone, heat shrinkable polyolefin, PTFE, FEP, metallic or othertubing that has a higher melting temperature than the assembledring-shaped elements. This method may further comprise the step ofcoating the tubular structure with an elastomeric adhesive ordispersion. In another aspect of the invention, the mandrel may have apre-formed curvature for accessing a specific region of a body cavity,the mandrel may include a collapsible, inflatable or dissolvable mandrelallowing the tubular structure to vary in diameter and lumen size, andthe mandrel may be formed of an electrically dissolvable epoxy resin.

In another aspect of the invention, a method of manufacturing a medicaltubing having a length with variable characteristics is disclosed, themethod comprising the steps of placing a plurality of ring-shapedelements upon a support member or mandrel in a series arrangement, andfusing the plurality of ring-shaped elements together over the supportmember or mandrel with a solvent or other chemical compound. In thismethod of the invention, the fusing step may further comprise the stepof immersing the ring-shaped elements into the solvent to fuse theelements.

In another aspect of the invention, a method of manufacturing a medicaltubing having a length with variable characteristics is disclosed, themethod comprising the steps of placing a plurality of ring-shapedelements upon a support member or mandrel in a series arrangement, andbonding together the plurality of ring-shaped elements upon a supportmember or mandrel with an adhesive. The adhesive may be photodynamic orheat-activated.

In another aspect of the invention, a method of manufacturing athin-walled tube is disclosed comprising the steps of coating a wirewith a plastic material, wrapping the coated wire around a mandrelforming a plurality of windings, and heating the wound coated wire untilthe plastic material melts and bonds the windings forming awire-reinforced tube. In this method of the invention, the plasticmaterial may comprise at least one of polyurethane, a thermoplasticmaterial and a thermoset material. In another aspect of the invention,the wire may comprise at least one of a metallic material and a secondplastic material, or the wire may be coated with the plastic material ina coextrusion process. This method of the invention may further comprisethe step of compressing the windings as the coated wire is being heated.

In another aspect of the invention, this method may further comprise thestep of providing a mold to compress the windings. This method mayfurther comprise the step of removing the wire-reinforced tube from themandrel after the tube is cooled. The wound-coated tube may also beheated until the plastic material is formed above, below and between allthe windings. This method may further comprise the step of dipping thetube in a solvent-based solution forming an outer layer of the tube. Inother aspects of the invention, the mandrel may be tapered to providethe tube with varying diameter throughout the length of the tube, thecoated wire may be alternatively wound with the filament around themandrel, the mandrel may be any shape such that the resultant shape ofthe tube may be removed from the mandrel after the heating step, and themandrel may be a multiple-part mandrel.

In another aspect of the invention, a method of manufacturing akink-resistant thin-walled tube having a length with differentcharacteristics is disclosed, the method comprising the steps of coatinga mandrel with a first layer of plastic material, placing a springreinforcement over the first layer, and coating the spring reinforcementwith a second layer of plastic material to form a spring-reinforcedtube. In this method of the invention, each of the first layer and thesecond layer may be formed in either an extrusion process or a moldingprocess. The spring reinforcement of the invention may be a pre-woundwire comprising at least one of a metallic material and a second plasticmaterial. The method of the invention may further comprise the step ofdipping the tube in a solvent-based solution forming an outer layer ofthe tube.

In another aspect of the invention, another method of manufacturing akink-resistant thin-walled tube having a length with differentcharacteristics is disclosed, the method comprising the steps of coatinga mandrel with a first layer of plastic material, placing a springreinforcement over the first layer, and dipping the spring-reinforcedfirst layer in a solvent based solution to form a second layer of thetube. In this method of the invention, the second layer is impervious,the mandrel may be tapered to provide the tube with varying diameterthroughout the length of the tube, and the mandrel may be any shape suchthat the resultant shape of the tube may be removed from the mandrel.

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a length of medical tubingaccording to a first embodiment of the invention;

FIG. 2 illustrates a perspective view of a single plastic ring of thetubing of the invention to be arranged in a series;

FIG. 3 illustrates a perspective view of the medical tubing of theinvention being formed according to a process of the invention;

FIG. 4 is a side view of a composite tube of the invention in a straightcondition;

FIG. 5 is a side view of the composite tube of FIG. 4 in a bentcondition;

FIG. 6 is an end view of the composite tube of FIG. 4;

FIG. 7 is a side view of a tube having a bending bias in accordance withanother embodiment of the invention;

FIG. 8 is an end view of the tube of FIG. 7 having a bending bias;

FIG. 9 is a side view of a wire-ring reinforced tube in a straightcondition in accordance with another embodiment of the invention;

FIG. 10 is a side view of the wire-ring reinforced tube of FIG. 9 in abent or circular condition;

FIG. 11 is an end view of the wire-ring reinforced tube of FIG. 9; and

FIGS. 12( a) and 12(b) illustrate perspective views of tubes havingvarying diameters in accordance with additional embodiments of theinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS AND BEST MODE OF THE INVENTION

A medical tubing is illustrated in FIG. 1 and is designated by referencenumeral 10. The medical tubing 10 is adapted for insertion into a bodytissue or cavity. The tubing 10 has a proximal end 12, a distal end 14,a length and at least one lumen 15. The tubing 10 is constructed of aplurality of individual, discrete, generally ring-shaped elements 16arranged in series to form a continuous tubular structure 18. FIG. 2illustrates a perspective view of a single generally ring-shaped plasticring 16 of the tubing 10 of the invention to be arranged in a series. Inone aspect of the invention, the ring-shaped elements 16 are formed of athermoplastic material. In another aspect of the invention, thering-shaped elements 16 are formed of a thermoset material. Thering-shaped elements 16 may be arranged in series and subsequently fusedor bonded by heat or chemical reaction to form a substantiallycontinuous form.

Referring to FIG. 5, it can be seen that tubing constructed from aseries of individual, discreet elements may be bent, shaped or coiledwithout kinking. In particular, the tubing 10 may have variablecharacteristics along the length. This may be achieved, for example, bythe use of the ring-shaped elements 16 to provide different flexuralmodulus. For instance, a length of tubing may be constructed whereinflexible ring-shaped elements are separated by rigid ring-shapedelements, i.e., a flexible portion of a tubular structure may be formedadjacent to a rigid or semi-rigid portion of the tubular structure toprovide variable flexibility. Such construction allows softer, moreflexible material to be displaced and stretched along a curvature sothat the rigid material is not deformed. A preferred embodiment maycomprise a thermoplastic of a very rigid nature spaced by a compatiblethermoplastic of a very soft nature. In other words, the ring-shapedelements 16 may be formed of two or more different materials havingdifferent chemical composition and hardness that are alternately fusedor bonded together to form a continuous tube having circumferentialportions that are alternately rigid and flexible.

Referring back to FIG. 3, there is shown a process of manufacturing themedical tubing 10 having variable characteristics of the invention wherea support member or mandrel 20 is used to hold an assembly ofring-shaped elements 16 in an elongate, series arrangement. Inparticular, the process of manufacturing the medical tubing 10 comprisesthe steps of placing the plurality of ring-shaped elements 16 upon thesupport member or mandrel 20 in a series arrangement; and heating theplurality of ring-shaped elements 16 to fuse them together over thesupport member or mandrel 20. Additional lumens may be incorporated intothe formed tubular structure 18 and supporting them with, e.g., anelongate wire. The arranged or assembled ring-shaped elements 16 arethen heated so that the ring-shaped elements 16 are fused together overthe mandrel(s) 20.

In another aspect of the invention, it is contemplated that a controltube is placed over the arranged or assembled ring-shaped elements 16prior to the application of heat. The control tube may comprise ofglass, silicone, heat shrinkable polyolefin, PTFE, FEP, metallic orother tubing that has a higher melting temperature than the assembledring-shaped elements 16. A silicone control tube may be placed over theassembled ring-shaped elements 16 as the control tube and the assembledring-shaped elements 16 are placed in an oven until the plasticring-shaped elements 16 have fused together. Alternatively, the mandrel20 may be heated until the thermoplastic ring-shaped elements 16 havefused together. The control tube and the mandrel(s) 20 are subsequentlyremoved from the tubing 10.

In another aspect of the invention, the ring-shaped elements 16 couldhave either an inner diameter or an outer diameter or a combination ofboth comprising of thermoplastic or applied thermoset material alongwith the mandrel 20. A compression sleeve of silicone tubing could beplaced over the structure and either heated or allowed to cure. Theresulting product once the compression sleeve is removed would be veryflexible and malleable and yet would have tremendous column strength.This structure and variants thereof would be applicable, e.g., to themalleable shaft graspers. In another aspect, the nested springs could bereplaced with U-joints of various types.

Alternatively, the process of the invention could be accomplished with athermoset material as follows. The spring wire is wound on the mandrelwith the desired pitch. It is then coated in the thermoset such assilicone. Next, the silicone compression tube is placed over the springwire and the assembly is allowed to cure. The tube is then removed fromthe silicone tube and mandrel. Springs can be pre-wound and can be madeof materials other than steel that would otherwise not tolerate the heatrequired to flow a thermoplastic.

In another aspect of the invention, the entire process can beaccomplished in the opposite manner to achieve the same results. Thismay be done by pre-winding a co-extruded wire into a spring andinserting it into a tube of desired diameter. A balloon or other suchmechanism for pressurizing the spring coil may be inserted as themandrel in the I.D. and the assembly are heated. As a result, thecompression member is on the inside and the static member is on theoutside.

It is appreciated that coating the mandrels with various types of lowfriction surfaces assist in the removal of the finished tube. Forexample, Teflon coatings and various mold releases have been found to beeffective.

Multiple lumens can also be easily included in the fusing or bondingprocess of the invention. This can be accomplished in numerous ways. Thefirst is to provide a groove in the winding mandrel and place astainless tube in the groove. The winding extrusion is placed on themandrel as before. When the resulting assembly is removed, the stainlesstube will be imbedded in the plastic of the wire extrusion. Another wayto accomplish multiple lumens is to wind separate mandrels with the wireextrusion and then instead of placing the silicone compression sleevearound each mandrel individually the mandrel assemblies are placed nextto each other and the compression sleeve is placed over both of them.Mandrels can be of a variety of shapes to give the lumens of theresulting tube different internal and external shapes. Another versionof this concept would be to assemble the mandrels with a strip orextrusion of plastic material (or non-plastic may work as well) inbetween the mandrels and then the assembled mandrels can have theextruded wire wound around them. The assembly would then be fused orbonded and the plastic in between the mandrels would form very thinwalled lumens.

As such, it is appreciated that lumens can be placed external orinternal to the main lumen of a catheter. Tremendous advantages inoverall size of the catheters can be achieved because unlikeconventional extrusion techniques which require that wall thickness bemaintained constant, the catheters of the invention can have wallthickness not only of localized thickness increases but also lengths orsections of different materials.

The tubing constructed according to the present invention is especiallyunique in that it may be constructed having an extremely thin wallsection. FIGS. 1-6 illustrate a relationship between a diameter of atube and a wall thickness of that tube. Normally, tubing having a largediameter (0.200″ or larger) and a very thin wall (0.015″ or less) isextremely subject to kinking when it is bent, coiled or twisted.However, tubing constructed according to the present invention does notkink under the same circumstances since the softer materials allowbending without deformation of the primary, rigid material. It can beseen that as the tubing is bent, shaped or curved, the rigid materialacts as a reinforcement to maintain the size and shape of the lumenwhereas the soft material stretches along the large arc and compressesalong the short arc. The stresses that normally accumulate along a thinwalled tube and cause it to kink are absorbed and distributed in thecomposite construction of the present invention so that the tubing doesnot kink. Kink-free tubing may be constructed having wall thickness todiameter ratios in excess of 20:1, which in a standard extrusion is notpossible. Wire coil reinforced tubing allows tubing to be made with avery thin wall. High diameter to wall ratios are possible when a wirecoil is used to reinforce an extruded tube. However, wire reinforcementcreates hysterisis and makes the formation of additional lumensproblematic. In addition, it requires that formation of the tubing bedone in a continuous form, not allowing for variations at specificregions along the length of the tubing.

In another embodiment of the invention, a method of manufacturing themedical tubing 10 having variable characteristics is disclosed, themethod comprising the steps of placing the plurality of ring-shapedelements 16 upon the support member or mandrel 20 in a seriesarrangement; and fusing the plurality of ring-shaped elements 16together over the support member or mandrel 20 with a solvent or otherchemical compound. That is, this embodiment contemplates the use ofsolvent materials to fuse the various ring-shaped elements 16 togetherto form the continuous tubular structure 18. The ring-shaped elements 16may be arranged or assembled upon the support member or mandrel 20 in adesired sequence for specific applications. Then, a solvent may beapplied to the assembled elements so that they are fused together toform a continuous length of tubing. In another aspect of the invention,the assembled elements 16 may be immersed into a solvent to fuse theelements.

In yet another embodiment of the invention, an adhesive may be used toadhere the various ring-shaped elements 16 together to form thecontinuous tubular structure 18. For instance, a heat-activated adhesivemay be formed as a ring-shaped element and placed between each of therigid and flexible ring-shaped elements 16. When heat is applied, theadhesive is activated and the ring-shaped elements 16 are bonded. Inanother aspect, a photodynamic adhesive may be used to bond thering-shaped elements 16. Such adhesives include epoxies that are curedby application of UV light. Other adhesives, such as cyanoacrylates andvarious rubber cements may be used to achieve specific results. Anotheraspect of the invention contemplates the use of a highly resilient,flexible rubber-like adhesive, such as silicone or other elastomericadhesive, to bond the rigid ring-shaped elements 16 together. Such aconstruction allows the bond to absorb and distribute the forces thatwould normally kink a large-diameter, thin-walled tube and maintain theshape of the lumen. For instance, a series of rigid ring-shaped elementsmay be loosely assembled upon a mandrel or form and subsequently coatedwith an elastomeric adhesive or dispersion. The elastomeric adhesivematerial that flows between the rigid ring-shaped elements forms aresilient, flexible region between the rigid elements. An alternateembodiment contemplates the use of metallic rings assembled upon amandrel and subsequently bonded together with a resilient, flexibleelastomeric adhesive. The bending characteristics of such a constructionmay be imparted by varying the length of the metallic ring-shapedelements. For instance, a semi-rigid portion may be comprised ofmetallic ring-shaped elements that are long in comparison to themetallic ring-shaped elements of a flexible portion. The metallicring-shaped elements of the flexible portion are shorter allowing atighter or smaller bending radius.

The tubing and process of manufacturing of the tubing of the inventionprovide a distinct advantage over extrusion in that a sensitive flexibleportion may be reinforced while less sensitive regions may be left aloneor un-reinforced. Additionally, there are many medical applicationswhere only a portion of the tubing should be flexible while otherportions should be rigid or semi-rigid. There are also applicationswhere a portion must be very soft and flexible but must also benon-compressible and kink-free and yet have a portion rigid enough toallow navigation through tortuous lumens. An example of conflictingrequirements include endoscope shafts, urinary, billiary and vascularcatheters as further described below. Many of these devices couldbenefit from a thin-walled tube that has a large primary lumen, one ormore secondary lumens and a very flexible portion that may be controlledby pull wire(s) or cable(s) within the secondary lumen(s).

Referring to FIG. 7, there is shown a length of tubing 30 according toanother embodiment of the invention having alternating ring-shapedelements 32 that are shaped to provide a preferred bending bias 36. Inthis embodiment, the more rigid ring-shaped elements 32 a are truncatedor wedge-shaped, as are the less rigid elements 32 b. A preferredarrangement of alternating truncated or wedge-shaped elements 32 a and32 b provides the preferred bending bias 36. Stated another way, thelarger flexible portion adjacent to the smaller rigid portion and isopposed to the smaller flexible portion adjacent to the larger rigidportion provides a bias toward the side having the larger flexibleportion when a compression load is applied. The opposite is the casewhen a tension load is applied. As can be seen from the figures, thebiasing arrangement may be formed adjacent to a rigid or semi-rigidarrangement of discreet, individual ring-shaped elements. FIG. 8illustrates an end view of the tube having the bending bias of FIG. 7.FIGS. 9 and 10 are side views of a wire-ring reinforced tube in astraight and in a bent condition, respectively, in accordance withanother embodiment of the invention, and FIG. 11 is an end view of thewire-ring reinforced tube of FIG. 9.

Referring to FIG. 12, a length of tubing 40 is shown having a firstdiameter 42 and at least a second diameter 44. The differing diametersare a product of assembling various ring-shaped elements 46 upon aforming mandrel and fusing the elements 46 together to form a continuoustube. It can be seen that many different arrangements of smaller,larger, softer and harder materials may be assembled in any number ofways. In addition, various colored elements may be arranged asindicators or radiopaque elements may be assembled along the length ofthe assembled tube. For example, a rigid portion of tubing may beproduced for a specific length at a specific diameter, followed by asemi-rigid portion at a second diameter (smaller or larger), followed bya very flexible portion at a third diameter (smaller or larger),followed by a rigid or semi-rigid portion at a fourth diameter (smalleror larger) and so on.

The present invention also contemplates the use of mandrels or formsthat may have curves or other useful forms or shapes that fit varioususes. For instance, guiding catheters may be constructed that havepre-formed curvatures for accessing specific anatomical regions of abody. Mandrels or forms may include collapsible, inflatable, dissolvableor the like that allow the tubular body to have variations in diameterand lumen size. As an example, a mandrel or form may be constructed ofan electrically dissolvable epoxy resin. The mandrel or form retains itsshape until an electrical impulse is applied. The material separatesupon application of electrical energy leaving a complex lumen shapewithin the tubular body.

The following is yet another example of a process for making thin-walledtubes of the invention:

(1) First, a mandrel of steel is machined to match the internal diameteror shape of the intended tube;

(2) Second, a stainless steel wire, e.g., of about 0.006″ in diameterhas a layer of polyurethane co-extruded onto it with a resultingdiameter of about 0.020″;

(3) The co-extruded wire is close wound around the length of the mandreland the ends are secured such that the resultant coil will not unwind;

(4) Fourth, a silicone tube with an inner diameter (I.D.) less than thatof the wound coil outer diameter (O.D.) is placed over the entireassembly such that it completely covers the wound coil;

(5) Fifth, the assembly is placed in an oven at approximately 180° C.for 15 to 30 minutes (this is for Pellethane; other plastics requiredifferent parameters.);

(6) Sixth, the assembly is removed from the oven and cooled. Thesilicone sheath is removed once the assembly has cooled; and

(7) Seventh, the wound coil is removed from the mandrel.

This process results in a tube with walls of about 0.015″ in thicknessand a reinforced coil of stainless wire embedded in it. The tube isvirtually un-kinkable and has very smooth inner and outer diametersurfaces. In addition, the mandrel can be tapered to provide a tube withvariable diameters from one end to the other. In other examples,physical properties of the resulting tube can be adjusted by varying thediameter of the wire, the diameter of the co-extruded plastic, the typeand properties of the wire and plastic such as chemical composition andhardness. The tolerance that can be held on the I.D. of the tube is veryhigh and on the order of 0.001″ or less. The tolerance on the O.D. iscomparable. The range of diameters for this process is quite large.Prototypes have been made from 0.026″ I.D. to 0.75″ I.D. and with wiresfrom 0.004″ diameter to 0.008″ inch diameter.

It should be noted that two or more different types of wire/plasticextrusions can be wound together and the wire is not a requirement forthis process to work. This process would be useful for molding thin walltubes to dimensions that are not practical or obtainable by extrusion ortraditional molding. Mandrels do not need to be round and could combineboth round and non-round shapes on the same mandrel.

The main requirement is that the resultant shape be capable of beingremoved from the mandrel once the heat cycle is finished. With unusualshapes this could be accomplished with split mandrels and sacrificialmandrels that could be removed by dissolving in acid by way of example.

The method of the invention may be applied in the construction of thefollowing products, at least in part if not in whole:

-   -   1. AV introducers: These devices are used to gain access to        blood vessels. The AV introducers of the prior art are typically        fairly thick walled flouropolymer about 2-3 inches long. The AV        introducers of the invention decrease wall thickness and at the        same time increase kink resistance. Vascular surgeons also use        longer versions of these to access various parts of the vascular        system and then use these sheaths to inject various medicants or        use them as a highway for the introduction and removal of        instruments. These longer versions can be 70 centimeters in        length or more and would benefit tremendously by the increased        kink resistance and flexibility that the AV introducers of the        invention would offer. More specifically, the sheath of the        invention would be capable of being coated internally as well as        externally with friction reducing coatings such as hydrophilic        coatings as well as heperanized coatings or other medically        beneficial surface treatment.    -   2. Urological sheaths: Different urological sheaths can be        produced by the methods of the present invention, e.g., ureteral        access sheaths, urethral and bladder access sheaths, and kidney        access sheaths modified to direct a scope for various        procedures.    -   3. Ureteral stents: These can be made with the process of the        invention and would have the benefits of thin walls, high column        strength and tremendous flexibility. The common wisdom in        urology is that thin flexible stents are more comfortable for        the patient but more difficult for the physician to place.        Larger more rigid stents are easier to place but uncomfortable        for the patient. The stent of the invention would be both small        and flexible and yet easy to place due to its inherent column        strength.    -   4. Trocar cannula: These can be made to be very thin walled and        yet flexible (or inflexible), and can be very resistant to        kinking or compressing. This may be achieved by the bonding or        fusing process of the invention with a braided structure instead        of a coil. In another aspect, a folded structure could be made        that would allow the cannula sheath to be inserted first        followed by the cannula itself.    -   5. Suction/Irrigation (S/I) tubing: Prior art S/I tubing is        currently made from PVC and is very thick walled to prevent the        tube from kinking or collapsing under vacuum. With the process        of the invention, the following benefits can be achieved—the        tubing would be kink resistant yet have thin walls and therefore        be lightweight, cost would be comparable to PVC without the        environmental concern, thus, it would reduce the overall amount        of plastic used. Currently, S/I tubes have 1 to 2 lbs of PVC        tubing in them. The S/I tubing of the invention would reduce the        overall weight of plastic to approximately 1/10 of a pound and        would be easier for the surgeon to use. In addition, the wire in        the irrigation tube could be electrically heated to allow the        fluid to be at or near body temperature when introduced to the        patient.    -   6. Insufflation tubing: This tubing is used to deliver carbon        dioxide gas for laparoscopic surgery and has some of the same        problems as S/I tubing. Lighter weight and less plastic wasteful        tubing could be made, and the heating element in the wall would        be of benefit to the patient by allowing body temperature gas to        be introduced instead of colder gas.    -   7. Vacuum tube: The process of the invention would be beneficial        to any situation, either medical or non-medical, where the need        exists for a vacuum tube to be thin walled and preferably kink        resistant. This process could also be used to produce thin        walled pressure tubes.    -   8. Split sheath introducers: The process of the invention can be        modified to make a split sheath introducer. The wire extrusion        can be wound on a special mandrel to make a semicircular tube on        each side of the mandrel and then fusing or bonding the split        sheath together.    -   9. Tracheostomy tubes: Thin walled kink-free tracheostomy tubes        would benefit from the process of the invention. The        balloon-filled lumen could be easily fused or bonded together        along with the breathing tube. The same advantages would apply        to crycothyrodectomy tubes used in emergency situations.    -   10. Intubation tubes: The intubation tubes have very thin walls        and are very kink resistant which would help enormously with        these devices especially in pediatrics or cases where the        trachea has become constricted. The flexibility would make them        ideal for nasal tubes as well.    -   11. G-tubes/J-tubes: Gastronomy and jujenostomy tubes are used        for enteral feeding and would likewise benefit from reduced        diameters, enhanced column strength for insertion, and kink        resistance for safety.    -   12. ERCP catheters: Extracoporeal retrograde        cholangeopancreatography catheters are very long catheters        typically used to treat gallstones in the cystic duct. These        would benefit from the increased column strength and reduced        wall thickness as well as high kink resistance.    -   13. Endoscope shafts: Flexible and steerable endoscopes require        shafts that can give good protection to the internal components        as well as provide regions of variable flexibility and good        column stiffness throughout. The shafts must also accommodate        multiple lumens.    -   14. Drainage tubes: Drainage and suction tubes would also        benefit from thin walls, lightweight and kink resistance.    -   15. Guide catheters: Guide catheters commonly used in cardiology        to gain access to the coronary arteries are carefully designed        to meet various design criteria such as shape, stiffness,        steerability, torque strength and kink resistance. They have to        be smooth and non-thrombogenic. The bonding and fusing process        of the invention can serve as a good basis of construction for        these devices. Torque strength or torqability can be improved in        devices of the invention by putting relatively stiff elements        along the length of the shaft or by altering the plastic used to        extrude over the wire.    -   16. Hydrocephalic shunts: A common problem with these shunts,        which are used to drain excess hydrocephalic fluid from the        ventricles of the brain, is that they can kink and prevent        adequate drainage. This in turn can require a revision to be        performed or merely patient discomfort and possibly increase the        chances of an infection. By producing portions of them with the        process of the invention, it is possible to create very crush as        well as kink resistant shunts.    -   17. Guidewires: Guidewires are used in a number of applications        including urology and radiology. They are commonly constructed        with close wound stainless steel springs and then coated with        Teflon or a plastic for lubricity. They are typically 2 to 6        feet long and are around 1 mm in diameter or less. These        structures can be fabricated with the process of the invention.    -   18. Angioplasty and dilation balloons: The catheters that these        balloons are placed on require the ability to transmit as much        as 15 atmospheres or more over a 3-foot or longer length. Here        again the advantages of reinforced thin walls with excellent        column strength would be very helpful.    -   19. Vascular grafts: A variety of graft designs are commonly        used and these include designs for aortic grafts, dialysis        grafts, bypass grafts, arterial grafts for various locations in        the peripheral vasculature. All of these will benefit from kink        resistance and crush resistance as well as excellent        flexibility. Various coatings and surface modifications can be        applied.    -   20. Cholangiography catheters: Catheters used to deliver        contrast media to the cystic duct are difficult to use as the        conflicting requirements of kink resistance and thin walls make        necessary a compromise. This is not the case with the tubing of        the invention where the wall can be kept very thin and kink        resistant.    -   21. Vascular embolectomy/thrombectomy catheters: These small        diameter catheters have balloons on them for removing clots and        in the case of thrombectomy they have a spring body which would        make the process of the invention a natural for them. As for the        embolectomy catheters, they may benefit from the educed profile,        increased inflation lumen and guidewire lumens.    -   22. Central venous catheters: These catheters are placed near        the clavicle and access the superior vena cava through one of        the subclavian or innominate veins. They are used for emergency        treatment in the case of kidney failure among other uses. These        catheters are frequently constructed with two and three lumens        and require the ability to extract and return blood quickly.        They would benefit from the processes of the invention in that        the walls can be made thinner for increased flow or reduced        profile or both. They would be almost kink proof and they would        have tremendous column strength which would aid in insertion.        The processes of the invention would not interfere with any of        the commonly used coatings and they may show up better on        ultrasound.

The foregoing disclosure and description of the invention areillustrative and explanatory thereof, and various changes in the size,shape and materials, as well as in the details of the illustratedconstruction, may be made without departing from the spirit and scope ofthe invention. For these reasons, the above description should not beconstrued as limiting the invention, but should be interpreted as merelyexemplary of preferred embodiments.

The invention claimed is:
 1. A method of manufacturing a medical tubinghaving a length with variable characteristics, the medical tubingcomprising a plurality of individual, discrete, generally ring-shapedelements arranged in series and fused together to form a continuoustubular structure, the method comprising the steps of: providing aplurality of ring-shaped elements; each ring-shaped element having anaperture located between an inner diameter and an outer diameter;passing a wire through the aperture of each ring-shaped element along asupport member or mandrel such that the wire is adjacent to the innercircumference of the plurality of ring-shaped elements and thelongitudinal axis of the wire is parallel to the longitudinal axis ofthe support member or mandrel; placing the plurality of ring-shapedelements upon the support member or mandrel in a series arrangement;heating the plurality of ring-shaped elements and wire to fuse the ringsover the wire and support member or mandrel; and removing the supportmember or mandrel.
 2. The method of claim 1, wherein the step of placingthe plurality of ring-shaped elements includes placing the plurality ofring-shaped elements upon the wire before the heating step.
 3. Themethod of claim 1, further comprising forming a control tube over theassembled ring-shaped elements prior to the heating step.
 4. The methodof claim 3, wherein the control tube comprises at least one of glass,silicone, heat shrinkable polyolefin, PTFE, FEP, metallic or othertubing that has a higher melting temperature than the assembledring-shaped elements.
 5. The method of claim 1 wherein the ring-shapedelements have either an inner diameter or an outer diameter comprised ofthermoplastic or thermoset material.
 6. The method of claim 1 furtherincluding the step of removing the wire.
 7. The method of claim 1wherein the step of placing the plurality of ring-shaped elementsincludes placing ring-shaped elements having different lengths.
 8. Themethod of claim 1 wherein the step of heating the plurality ofring-shaped elements includes fusing the ring-shaped elements closer orfurther apart.
 9. The method of claim 1 further including the step ofproviding a pull wire.
 10. The method of claim 1 wherein the step ofheating the plurality of ring-shaped elements and wire includes the stepof heating the plurality of ring-shaped elements to fuse the rings overthe wire and support member or mandrel to form a first lumen and asecond lumen.